Method and circuit configuration for generating filter coefficients

Abstract

Coefficient signals are generated for a transverse filter which receives data signals assuming W different amplitude values as input signals, with N successive input signals being stored in a serial-in-parallel-out (SIPO) storage arrangement having N storage cells. According to the input signals stored in the storage cells of the SIPO storage arrangement, predetermined filter signal coefficients possible for the W possible amplitude values individually are added and W corresponding partial sum signals made available. The partial sum signals are each multiplied by a factor corresponding to the particular amplitude value and subsequently added to form a sum signal. At least some of the product signals are multiplied by an additional correction signal coefficient assigned to the particular amplitude value. The additional product signals resulting therefrom are included in the formation of the sum signal.

What is claimed is: 
     
       1. A method for generating filter signals in a transversal filter, to which data signals assuming a plurality W of different amplitude values are supplied as input signals, said method comprising the steps of: storing a plurality N of successive input signals in a serial-in-parallel-out storage arrangement having a plurality N of data signal storage cells;   adding predetermined filter signal coefficients corresponding to the input signals stored in the data signal storage cells individually for the W possible amplitude values and making available W corresponding partial sum signals;   multiplying the partial sum signals individually by a factor corresponding to the particular amplitude value to form product signals;   multiplying at least some of the product signals by an additional filter coefficient assigned to the particular amplitude value to form additional product signals; and   adding the product signals and the additional product signals to form a filter signal.   
     
     
       2. The method of claim 1, further comprising the step of: setting the additional filter signal coefficients adaptively upon the forming of a filter signal according to the product signal just present associated to this filter signal and a data signal corrected by the just formed filter signal.   
     
     
       3. A method for generating correction signals in a transmission equipment for a duplex transmission of data signals via a two-wire line, which data signals assume a plurality W of different amplitude values and which correction signals function for suppressing echo signals relating to transmit data signals delivered to said two-wire line and superimposed on receive data signals coupled from said two-wire line, said method comprising the steps of: storing a plurality N of successive transmit data signals in a serial-in parallel-out storage arrangement having a plurality N of data signal storage cells;   adding predetermined correction signal coefficients corresponding to the transmit data signals stored in said data signal storage cells individually for the W possible amplitude values and making available W corresponding partial sum signals;   multiplying the partial sum signals individually by a factor corresponding to the particular amplitude value to form product signals;   multiplying at least some of the product signals by an additional correction signal coefficient assigned to the particular amplitude value to form additional product signals; and   adding the product signals and the additional product signals to form a correction signal.   
     
     
       4. The method of claim 3, further comprising the step of: setting the additional correction signal coefficients adaptively upon the forming of a correction signal according to the product signal just present associated to said additional correction signal and a receive data signal corrected by the just formed correction signal.   
     
     
       5. A transversal filter for generating filter signals, to which data signals assuming a plurality W of different amplitude values are supplied as input signals, said transversal filter comprising: a serial-in-parallel-out storage arrangement having a plurality of N data signal storage cells for storing N successive data signals;   a coefficient storage arrangement having a plurality of N coefficient storage cells for storing filter signal coefficients assigned to the N data signal storage cells;   polling means connected to the serial-in-parallel-out storage arrangement and the coefficient storage arrangement for polling the data signal storage cells together with the coefficient storage cells;   an accumulator arrangement with a plurality W of accumulators, each of which is assigned to one of the possible W amplitude values of said data signals and is individually selectable according to the data signals stored in the data signal storage cells at the polling of the data signal storage cells and the coefficient storage cells, thereby adding only the filter signal coefficients provided by the coefficient storage arrangement for the particular amplitude value and making available a corresponding partial sum signal;   a multiplier arrangement with a plurality W of first multipliers, each of which is coupled to one of the accumulators for multiplying the partial sums signal supplied to it by a factor corresponding to the particular amplitude value and makes available a product signal resulting therefrom;   a plurality of second multipliers succeeding at least some of the first multipliers for multiplying the product signal supplied to the particular second multiplier by an additional filter signal coefficient assigned to the particular amplitude value to form an additional product signal; and   an adder responsive to the product signals and additional product signals made available by the first and second multipliers which adder adds these product signals and additional product signals to form a filter signal.   
     
     
       6. The transversal filter of claim 5, wherein said serial-in-parallel-out storage arrangement comprises a shift register arrangement with N stages for storing the amplitude values of said data signals in a binary encoded form, wherein in the course of a polling cycle said polling means access the N stages for calling up the particular stored amplitude values successively and said coefficient storage arrangement for calling up the filter signal coefficients assigned by the particular stages: wherein upon the calling up of an amplitude value in conjunction with a filter signal coefficient the accumulator of said accumulator arrangement assigned to the particular amplitude value is activated for accepting the particular filter signal coefficient to form a partial sum signal;   and wherein buffer means responsive to a control signal output by said polling means and indicating the end of a polling cycle are connected with said accumulator arrangement which buffer means output the partial sum signals formed by said accumulator arrangement to said first multipliers only at the end of a polling cycle.   
     
     
       7. The transversal filter of claim 5, wherein said accumulator arrangement comprises a plurality of individual partial sum storage circuits for storing said partial sum signals; a multiplex arrangement connected at its input side with output terminals of the individual partial sum storage circuits and controlled by said amplitude values called up in the course of a polling cycle for selectively providing the partial sum signals stored in the individual partial sum storage circuits at an output terminal;   an adder connected at its input side with the output terminal of the multiplex arrangement and said coefficient storage arrangement for adding the filter signal coefficient called up from the coefficient storage arrangement and the partial sum signal just provided by the multiplex arrangement and providing a changed partial sum signal at its output terminal and a demultiplex arrangement connected at its input terminal with the output terminal of the adder and at its output terminals with input terminals of the individual partial sum storage circuits and controlled by said amplitude values called up in the course of a polling cycle for storing the changed partial sum signals provided by the adder in the individual partial sum storage circuits.   
     
     
       8. The transversal filter of claim 5, further comprising: one or more control devices, corresponding to the number of said second multipliers, for adaptively setting of the particular additional filter signal coefficient, each of the control devices is responsive to the product signal supplied to the particular second multiplier and to a data signal corrected by the just formed filter signal for calculating and supplying an additional filter signal coefficient in dependence upon the additional filter signal coefficient previously supplied to the particular second multiplier.   
     
     
       9. A transversal filter for generating filter signals, which is supplied with four-level binary encoded data signals of whose two possible amplitude values are symmetrical to a predetermined reference value and differ only with respect to sign, comprising: a serial-in-parallel-out storage arrangement having a plurality of N data signal storage cells for storing N successive data signals;   a coefficient storage arrangement having a plurality of N coefficient storage cells for storing filter signal coefficients assigned to the N data signal storage cells;   polling means connected to the serial-in-parallel-out storage arrangement and the coefficient storage arrangement for polling the data signal storage cells together with the coefficient storage cells;   an accumulator arrangement with two accumulators, each of which is assigned to one of said possible two amplitude values deviating from each other with respect to magnitude and which is individually selectable according to the data signals stored in the data signal storage cells at the polling of the data signal storage cells and the coefficient storage cells, thereby, dependent upon the sign information contained in the binary encoded data signals, accumulating only the filter signal coefficients provided by the coefficient storage arrangement for the particular amplitude value and making available a corresponding partial sum signal;   a multiplier arrangement including two first multipliers, each of which is coupled to one of the accumulators for multiplying the partial sum signal supplied to it by a factor corresponding to the particular amplitude value and makes available a product signal resulting therefrom;   a second multiplier succeeding one of said first multipliers for multiplying the product signal supplied to the second multiplier by an additional filter signal coefficient assigned to the particular amplitude value to form an additional product signal; and   an adder responsive to the product signals and the additional product signal made available by the first and second multipliers which adder adds these product signals and additional product signal to form a filter signal.   
     
     
       10. The transversal filter of claim 9, wherein said accumulator arrangement comprises two individual partial sums storage circuits for storing said partial sum signals; a multiplex arrangement connected at its input side with output terminals of the individual partial sum storage circuits and controlled by said amplitude values called up in the course of a polling cycle for selectively providing the partial sum signals stored in the two partial sum storage circuits at an output terminal;   an arithmetic arrangement at its input side with the output terminal of the multiplex arrangement and said coefficient storage arrangement for adding the filter signal coefficient called up from the coefficient storage arrangement and the partial sum signal just provided by the multiplex arrangement or for subtracting the filter signal coefficient called up from the coefficient storage arrangement from the partial sum signal just provided by the multiplex arrangement in dependence upon said sign information contained in the data signal just called up by said polling means and providing a changed partial sum signal at its output terminal and a demultiplex arrangement connected at its input terminal with the output terminal of the adder and at its output terminals with input terminals of the individual partial sum storage circuits and controlled by said amplitude values called up in the course of a polling cycle for storing the changed partial sum signals provided by the adder in the individual partial sum storage circuits.